A vertical rectangular tank is divided into two chambers whose horizontal sections are $2\mathrm{.}5$ and $5$ sqm$.,$ respectively.

The dividing wall is provided with a $150$mm by $150$mm hole located $0\mathrm{.}5$m from the bottom and whose coefficient of discharge is $0\mathrm{.}60.$ Initially there is $5\mathrm{.}5$m deep of water in the smaller chamber and $1$ m deep in the larger chamber.

What is the difference in the water level $($meters$)$ in the two chambers after $1\mathrm{.}25$ minutes?